The Presentations package at my web site ($50) has an Arrow3D routine. In
the Presentations graphics paradigm it is very easy to combine various
curves and objects in a graphic - you just draw one thing after another.
(Also in your Manipulate plot the PlotRange should be explicitly specified
so that each frame will have the same plot range.) So here is your helix
with an arrow with a Red tip going from the origin to the tip of the curve.
In this case I used an "Absolute" scaling so the arrowcone would always be
the same size.
Needs["Presentations`Master`"]
Manipulate[
Draw3DItems[
{ParametricDraw3D[{Sin[u], Cos[u], u/10}, {u, 0, t}],
Red,
Arrow3D[{0, 0, 0}, {Sin[t], Cos[t], t/10}, {.2, .7, "Absolute"}]},
PlotRange -> {{-1, 1}, {-1, 1}, {0, 2}},
Axes -> True],
Style["Helix with Arrow to Tip", 16],
Delimiter,
{t, 1, 20, Appearance -> "Labeled"}]
--
David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/
"Fabian" <fabian.uriarte at gmail.com> wrote in message
news:gbl2ve$lvl$1 at smc.vnet.net...
> Dear Group-
>
> In this plot:
>
> Manipulate[
> ParametricPlot3D[{Sin[u], Cos[u], u/10}, {u, 0, t}], {t, 1, 20}]
>
> Is there a way a to show an Arrow from the origin to the tip of the
> curve at all instances of time t?
>
> Thank you.
>